As the dosage form of vaccine preparations, most of the commercial products that are currently available are injections.
Existing vaccine preparations, for example, common influenza vaccine preparations that are used in Japan do not contain an adjuvant, and the effect thereof is not sufficient. There is also a case where the condition of a patient infected with influenza becomes serious even though the patient has received such a vaccine preparation.
Also, there exists a human papillomavirus vaccine product containing monophosphoryl lipid as an adjuvant. However, it is the actual circumstance that the monophosphoryl lipid is obtained by removing a sugar chain part of a lipopolysaccharide derived from Salmonella typhimurium for improving the safety, and thus the effect as an adjuvant is attenuated.
Therefore, an adjuvant containing a lipopolysaccharide derived from a bacterial species that is relatively safe and capable of achieving both high safety and the effect of stimulating immunity has been strongly demanded.
For example, Patent Literature 1 proposes a lipopolysaccharide (LPS) derived from Pantoea bacteria, and describes that the LPS is safer than conventional LPSs, and the immune reaction is enhanced when it is administered together with an antigen.
Patent Literature 1, however, lacks distinct reference and illustration regarding the use for acquired immunity, and also lacks reference to the optimum ratio of adjuvant/antigen.
Also, for example, Patent Literature 2 proposes a vaccine containing a combination of Poly(I:C) and zymosan as an inactivated antigen of a pathogen, and an immunostimulant (adjuvant), and describes an example of using a lipopolysaccharide (LPS) derived from Pantoea agglomerans as an adjuvant, and an influenza virus as a pathogen.
In the example of the vaccine containing a lipopolysaccharide (LPS) derived from Pantoea agglomerans described in Patent Literature 2, the vaccine is administered to a nasal mucous membrane, and there is no teaching about injection administration. Generally, it is the common knowledge in the art that the effective adjuvant differs depending on the administration site. Therefore, it is unclear whether a lipopolysaccharide (LPS) derived from Pantoea agglomerans is effective by injection administration from the example of the vaccine containing a lipopolysaccharide (LPS) derived from Pantoea agglomerans described in Patent Literature 2.